1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium incorporating therein a magnetic film and a protective film abounding with corrosionproofness formed on the front side of the magnetic film.
2. Description of the Prior Art
In recent years, research efforts have been emphatically devoted to the development of magnetic recording media incorporating therein an alloy magnetic film of high recording density. Among them is counted a magnetic recording medium which has a magnetic film formed on the surface of a substrate and a protective film further deposited on the magnetic film.
It is known to the art that this protective film can be made of any of various substances including metals such as osmium, ruthenium, iridium, manganese, and tungsten, oxides such as silicon oxide, titanium oxide, tantalum oxide, and hafnium oxide, various nitrides, carbides, boron, carbon, alloy of carbon with boron, polysilicic acid, and diamond-structure carbon (Japanese Patent Application Laid-open No. SHO 59(1984)-61,106).
Among the substances enumerated above, carbon enjoys popular acceptance for its excellent lubricating property. The protective film of carbon, however, exhibits relatively high permeability to H.sub.2 O and O.sub.2. It, therefore, is slightly deficient in the inherent protective function of conferring enhanced resistance to corrosion and weather conditions upon the magnetic film.
The protective films made of substances other than carbon are more or less superior in resistance to corrosion and weather conditions but are fairly inferior in lubricating property, to the protective film of carbon.